U.S. Pat. No. 5,279,401 granted to Eugen Stall Jan. 28, 1994 discloses in connection with FIG. 1 of the patent, a bevel gear, limited slip differential 108 that includes a friction clutch 121 for limiting the slip between an input ring gear 120 and an output side gear 116. An axial force is applied to the friction clutch by an actuating ring 128 that is displaced axially by a rotatable back-up ring 163. Back-up ring 163 is rotated by an electric motor 133 via pinion gear 135. Electric motor 133 is mounted on the cover of the differential housing 111 and drives pinion gear 135 by a radial shaft that extends through the cover into the housing 111. Electric motor 133 is controlled by signals indicating vehicle wheel slippage.
U.S. Pat. No. 5,279,401 granted to Eugen Stall Jan. 28, 1994 also discloses in connection with FIG. 2 of the patent, a planetary gear, limited slip differential 208 that includes a friction clutch 221 for limiting the slip between an input ring gear 220 and an output planetary carrier 216. An axial force is applied to friction clutch 221 by a ball ramp device comprising a rotatable and axially displaceable actuating ring 228 (that is displaced axially when rotated), a back-up ring 254 and intervening balls 249 that engage confronting ramps on the two rings. Actuating ring 228 is rotated by an electric motor 233 via pinion gear 235 at the end of a longitudinal shaft that is disposed in a passage that leads to the interior of housing 211. Electric motor 233 is mounted on the differential housing 211 and drives the shaft by a reduction gear set 232, 236. Electric motor 233 is controlled by signals indicating vehicle wheel slippage.
U.S. Pat. No. 6,571,928 B1 granted to Theodor Gassmann Jun. 3, 2003 discloses ball ramp engagement mechanisms in FIGS. 2, 3 and 4-6 for actuating a friction clutch in a limited slip differential. The ball ramp engagement mechanism of FIG. 2 is driven by an electric motor 58 via a reduction gear 60 that includes a spur gear that acts on a sector gear 56. The ball ramp engagement mechanism of FIG. 3 is driven by an electric motor via a reduction gear that includes a spur gear 76 that acts on a rack 74 which is an integral part of ball ramp disc 66. The ball ramp mechanism of FIGS. 4-6 is a double stage mechanism that includes a ball ramp disc 92 that is driven by a reduction gear 100 similar to the arrangement of FIG. 2.
U.S. Pat. No. 6,578,693 B2 granted to Nikolaus Mayr Jun. 17, 2003 discloses an axial setting device (ball ramp mechanism) comprising a setting disc 11 a pressure disc 17 and intervening balls 23 that engage confirmatory ramps of the discs 11, 17. Disc 11 is rotated by a worm gear 15 that is arranged tangentially with respect to the setting disc 11. Worm gear 15 is driven by electric motor 25.
U.S. Pat. No. 5,279,401; U.S. Pat. No. 6,571,928 B1; and U.S. Pat. No. 6,578,693 B2 are hereby incorporated in their entirety by reference.